Please note for the following tables “Threshold criteria” is defined as “A set of defined weather or environmental parameters, and their associated values, related to a known hazard that are used as a level marker for the beginning of and ending of a weather or environmental instance of a hazard, for which an alert is normally issued.”

Blizzard

When winds of 40 km/hr or greater are expected to cause widespread reductions in visibility to 400 metres or less, due to blowing snow, or blowing snow in combination with falling snow, for at least 4 hours.

Flash Freeze

When significant ice is expected to form on roads, sidewalks or other surfaces over much of a region because of the freezing of residual water from either melted snow, or falling/fallen rain due to a rapid drop in temperatures.

Issued when humidex value or temperature expected to reach 40 for at least one hour.

Warning

Quebec, except Nunavik*

Issued when the humidex value is 40 or greater and when the temperature is 30°C or warmer, and both conditions persist for at least one hour.OrIssued when temperature is 40°C or greater

Warning

Ontario - Extreme southwest (Essex and Chatham-Kent Counties)

Issued when 2 consecutive days of daytime maximum temperatures are expected to reach 31°C or more and nighttime minimum temperatures are expected to fall to 21°C or more. OrIssued when 2 consecutive days of humidex values are expected to reach 42 or more.

Warning

Ontario - Remainder of southern Ontario (including the District of Parry Sound)

Issued when 2 consecutive days of daytime maximum temperatures are expected to reach 31°C or more and nighttime minimum temperatures are expected to fall to 20°C or more. OrIssued when 2 consecutive days of humidex values are expected to reach 40 or more.

Warning

Ontario - North

Issued when 2 consecutive days of daytime maximum temperatures are expected to reach 29°C or more and nighttime minimum temperatures are expected to fall to 18°C or more. OrIssued when 2 consecutive days of humidex values are expected to reach 36 or more.

Warning

Saskatchewan, Manitoba, Northwest Territories and Nunavut

Issued when humidex value or temperature expected to reach or exceed 40°C.

Hurricane

When, within the following 36 hours, a hurricane or a developing hurricane is expected to pose a possible threat, with the risk of hurricane force winds (average sustained winds of 118 km/h or higher) threatening the area.

Warning

National, including all coastal and inland regions

When hurricane-force gales (average sustained winds of 118 km/h or higher) caused by a hurricane, or a strong tropical storm that may strengthen to hurricane force before making landfall, are expected to occur in 24 hours or less. It may also include areas where storm surge or exceptionally high waves are expected, even though winds may be less than hurricane force.

When there is a brief period (less than one hour) of very poor visibility (400 m or less), caused by heavy snow and blowing snow, and accompanied by strong, gusty winds of 45 km/h or greater, is expected to occur with the passage of a cold front.

Storm Surge

Nova Scotia, New Brunswick, Prince Edward Island, Newfoundland and Labrador, Quebec - along the St. Lawrence and Gulf of St. Lawrence coastal areas and the Magdalen Islands

Issued for abnormally high water levels and high waves (storm surge or storm tide) caused by storms, which have the potential to cause coastal flooding. This usually occurs when astronomical tides are at their maximum.

Tropical Storm

When, within the following 36 hours, a tropical storm or a developing tropical storm is expected to pose a possible threat, with the risk of tropical-storm force winds (average sustained winds of 63-117 km/h) threatening the area. This watch could be issued for:

Weather

A generic weather advisory.One example might be on days when funnel clouds are expected, but a Tornado alert would not be appropriate.

Warning

National, except Nunavik*

A generic weather warning may be issued for extreme weather events for which there is no suitable warning type, because they rarely occur.

A generic weather warning may also be issued for other weather events during situations where the environment is vulnerable due to pre-existing conditions and any further weather could result in a significant hazard. For example: 50 km/h winds following an ice storm which could cause structural wind damage.

A generic weather warning may also be issued for situations where the event is not expected to reach warning criteria values, but there is a special reason for the warning. For example: the first event of the season, or an off-season event.

Additional information in all alerts

The alert statements will include impact and call-to-action statements, designed to help Canadians be more aware of the risk of severe weather. This will allow them to take appropriate action to protect themselves, their families and their property.

A Call to Action statement provides information on how Canadians can protect themselves, family or property in this specific set of circumstances – some examples of a Call to Action statement are:

Strong winds can cause unusually high waves. Keep a safe distance from the waterfront to avoid being swept away.

It is recommended to stay indoors. If this is not possible, limit time spent outdoors and exposure to the cold as much as possible to reduce the risk of frostbite and hypothermia.

Public Safety Canada encourages everyone to make an emergency plan and get an emergency kit with drinking water, food, medicine, a first-aid kit and a flashlight.

An Impact statement is designed to indicate what could happen if the forecast conditions occur – some examples of an Impact statement are:

Surfaces such as highways, roads, walkways and parking lots will become icy, slippery and extremely hazardous.

Be prepared for winter conditions at higher elevations.

Twitter hashtags, such as #bcstorm and #ONstorm will also be included in the alert statements so that Canadians can report local severe weather observations to Environment Canada. Note that hashtags are case-insensitive.

Appendix A - Map of the Treeline in Canada

A map of Canada on which the green highlighted area represent the coverage of trees. All regions of Canada can support the growth of trees except in the extreme northern areas of the Yukon, Northwest Territories, Nunavut, Northern Quebec, and Labrador where the influences from the Arctic Circle and Hudson Bay move the treeline southward. This area of no growth creates an "U" shaped area on the map.